This mattress protector is great for that thick oversized mattress. We have the extra pillow top and it’s always hard to find the deep protectors or sheets for it.The material and elastic ends are so nice and snug the sheet went right over. Finally a superior product for my bed. Came back to edit my review after a fast response from the seller. The bottom layer is TPU and polyester and is indeed waterproof! I'm adding two stars because the mattress pad is soft and comfortable with the waterproof layer, which is hard to find.Original review: The seller repeatedly replies to questions and lists in the description that this mattress protector contains waterproof TPU lining, but I can't figure out if that's true. The bottom layer is quite obviously polyester, but I THINK I can feel some kind of liner underneath. The tag doesn't list polyurethane, though. I just hope it truly is waterproof, or at least thick enough to absorb any accidents from my 2 kids. It’s really waterproof! And it has good quality, after washing, it didn’t turn small, this is pretty good. IT DOESN'T make a sound! It stays put when changing sheets! It's AWESOME!!!! It definitely has a cooling effect. It does stretch a little out of shape in certain areas. But I just tuck it as tight as I can. Overall I like it very much. I bought a new mattress a while back off Amazon and realized if I wanted it to last longer I should probably get a cover for it. One of my coworkers had purchased this one and recommended it because it doesnt get warm. I'm pleased with my purchase after sleeping on it a few nights. I have bought three waterproof Mattress Protector Pad Cover altogether,and this is the best one.High quality, value for money. Packaging is good. Front material looks great. Back material looks waterproof although I didn’t test it specifically. Fits perfectly in size and beautifully in appearance on my full size mattress. May come back and buy another one if I ever change mattress, esp to different size.